It seems like the granularity of the node selection policy Tor can
implement to frustrate Sybils is partly a function of the size and
diversity of the Tor network. As long as there are ORs on at least 3
different IPs, a /32 restriction can work (an OP can still build a
circuit); as the network grew, you could start doing /16. As the
granularity of the policy coarsens, it becomes more difficult for Sybil
to succeed (she now has to have fingers in ever more distant pies).
Is autonomous system number a better indicator of network ownership than
host or network address? Is it also more delightfully coarse? Can the
current Tor network sustain such a policy (i.e., route only through
networks with distinct ASNs)? Am I sniffing glue?
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http://hemiolesque.blogspot.com/http://www.noncombatant.org/